Apparatus and method for an automated cetane number determination

In an apparatus and method for determining the cetane number of a fuel by combustion of a sample in a constant volume combustion chamber filled with compressed air into which the fuel is injected via a temperature controlled injection nozzle, wherein means are provided for sensing the pressure in the combustion chamber and recording it for determining the cetane number therefrom, an automated sample supplier is provided adapted to accommodate a plurality of fuel samples and including means for selectively connecting a pump to a particular sample and pressurizing it for injection into the combustion chamber and means for heating the combustion chamber and means for cooling the injector nozzle are provided for maintaining these devices at desired temperatures.